A136592 Column 2 of triangle A136590.

1, 3, -13, -10, 394, -2016, -5076, 170064, -1155024, -5005440, 193724640, -1656720000, -10280355840, 465087087360, -4804977542400, -39012996556800, 2035558551398400, -24660231399014400, -248246498826547200, 14713557956794368000

Offset

2,2

Links

Table of n, a(n) for n=2..21.

Formula

E.g.f.: A(x) = log(1 + x + x^2)^2 / 2!.

Example

E.g.f.: A(x) = 1*x^2/2! + 3*x^3/3! - 13*x^4/4! - 10*x^5/5! + 394*x^6/6! +...

Mathematica

With[{nn=30}, Drop[CoefficientList[Series[Log[1+x+x^2]^2/2, {x, 0, nn}], x] Range[ 0, nn]!, 2]] (* Harvey P. Dale, Feb 28 2013 *)

Prog

(PARI) a(n)=(n+2)!*polcoeff(log(1+x+x^2 +x*O(x^(n+2)))^2/2!, n+2)

Crossrefs

Cf. A136590, A136591, A136593, A136594.

Sequence in context: A273025 A273122 A071708 * A351657 A340441 A085416

Adjacent sequences: A136589 A136590 A136591 * A136593 A136594 A136595

Keyword

sign

Author

Paul D. Hanna, Jan 10 2008

Status

approved